The present disclosure is directed to an abrasive insert for a drilling machine such as a drill bit or other wear applications. It is typically an insert which is formed of very hard material, and which is equipped with a superhard polycrystalline or CBN layer on the leading edge or face of the insert. It is not uncommon to place superhard polycrystalline or CBN material on the end of an insert which bears against the rock formations being drilled by the drill bit so that the cap bears the brunt of the impact during drilling operations. This rather common arrangement enables the insert to last much longer. Typically, the superhard layer of polycrystalline or CBN is attached by sintering at selected extremely high temperatures or pressures. The interface between the layer and the hard material insert is a location at which substantial stress is concentrated, and it may well fail at the unwanted stress concentrations in that area. When that occurs, the stress concentration is sufficient to fracture the cap or face material at the interface. Also, the stresses can build up in the polycrystalline or CBN and cause fracture elsewhere in the polycrystalline or CBN cap.
The preferred superhard materials include polycrystalline or CBN. The polycrystalline material is manmade diamond, and more particularly polycrystalline diamond compact, a material formed to a desired shape and having characteristics of diamond. In other words, it is diamond like in hardness and other physical characteristics. Another hard material is CBN, more precisely, cubic boron nitride.
The polycrystalline or CBN cap formed on the insert has many advantages. With these advantages, there is one major detrimental aspect which primarily relates to the brittleness of the polycrystalline material. In other words, the polycrystalline cap is typically brittle and susceptible to fracture when stress is concentrated. To overcome this, the present disclosure proposes to provide a reinforcing structure within the polycrystalline layer so that the polycrystalline material has modified performance characteristics on the insert. The advance of the present invention particularly focuses on changing the polycrystalline layer. As before, the polycrystalline material is installed as manufactured. It is formed typically as a circular cap on the end of the insert. Even more so, it is able to handle the stresses which are encountered by virtue of the incorporation of reinforcing material within the polycrystalline cap. In this particular disclosure, the polycrystalline material is provided with a centralized disc. This disc is included fully surrounded by the polycrystalline material. This disc is incorporated completely within the polycrystalline material. It has the form of one or more circular reinforcing members which are comparable in shape to the polycrystalline disc but the reinforcing disc in the polycrystalline layer is preferably spaced so that it is approximately at the center position. It is preferably round and smaller than the polycrystalline layer. It is preferably formed of a material which is sufficiently ductile or bendable to avoid breaking. The ductility is greater in this embodiment. One material is high cobalt content cemented tungsten carbide or the like. It is able to withstand substantial flexure and does not work harden with time. The reinforcing insert in the polycrystalline material carries stress in the polycrystalline layer to the reinforcing member. This reinforcing member is constructed and installed so that the relief mechanism is in the polycrystalline disc.